Method of managing multimedia broadcast multicast service reception and related communication device

ABSTRACT

A method of managing MBMS reception for a communication device in a wireless communication system includes the step of performing discontinuous reception with off durations and receiving data of a MBMS subframe when the communication device has subscribed a MBMS service and the MBMS subframe is in one of the off durations.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a divisional application of U.S. application Ser. No.12/822,185, which claims the benefit of U.S. Provisional Application No.61/221,094, filed on Jun. 29, 2009 and entitled “Methods for receivingnon-MBMS data and MBMS data in wireless communications system”.

BACKGROUND OF THE INVENTION

1. Field of the Invention

A method used in a wireless communication system and relatedcommunication device are provided, and more particularly to, a method ofmanaging multimedia broadcast multicast service (MBMS) reception in awireless communication system and related device.

2. Description of the Prior Art

A long-term evolution (LTE) system, initiated by the third generationpartnership project (3GPP), is now being regarded as a new radiointerface and radio network architecture that provides a high data rate,low latency, packet optimization, and improved system capacity andcoverage. In the LTE system, an evolved universal terrestrial radioaccess network (E-UTRAN) includes a plurality of evolved Node-Bs (eNBs)and communicates with a plurality of mobile stations, also referred asuser equipments (UEs).

Over past few years, a multimedia broadcast multicast service (MBMS) hasbeen introduced in LTE specification. MBMS gives the opportunity tobroadcast TV, film, information such as free overnight transmission ofnewspaper in digital form and other media in these networks. Thebroadcast capability enables to reach unlimited number of users withconstant network load. Further, it also enables the possibility tobroadcast information simultaneously to many cellular subscribers.

Two important scenarios have identified for MBMS. One is single-cellbroadcast, and the second is MBMS Single frequency network (MBSFN).MBSFN is envisaged for delivering services such as Mobile TV, using theLTE infrastructure. In MBSFN the transmission happens from atime-synchronized set of eNBs, using the same resource block. The MBSFNtransmission takes place on dedicated subframes referred to as MBSFNsubframes, which would be used for other purpose than MBMS. For example,the UE reads a physical downlink control channel (PDCCH) grant on theMBSFN subframes for possible uplink scheduling. Namely, the MBSFNsubframes may be used for non-MBMS transmission when the MBSFN subframesare not allocated for MBMS data.

In order to support the UE to receive MBMS data, the eNB provides the UEwith information about which MBSFN subframes are used for MBMS controlchannel (MCCH), which MBSFN subframes are used for Multicast trafficchannel (MTCH) and which MBSFN subframes are used for dynamic schedulinginformation. In addition, the eNB provides resource allocations (e.g.modulation and coding schemes (MCSs) and frequencies) for MCCH, MTCH anddynamic scheduling information in broadcast message, for example, systeminformation.

However, when the UE subscribing the MBMS service receives a downlinkassignment (DL) indicating the MBSFN subframe on PDCCH, for exampledynamic scheduling or persistent scheduling, i.e. SPS, the specificationdoes not specify how the UE should decode the MBSFN subframe. Decodingthe MBSFN subframe with information/allocation not matching with whatthe eNB uses for encoding the MBSFN subframe causes decoding errors.

Apart from that, in the LTE system, a discontinuity reception (DRX)function has been introduced. The DRX function allows the UE to enter astandby mode during off durations (i.e. opportunity for DRX) of DRXcycles and during the off durations, stopping monitoring the PDCCH, soas to reduce power consumption of the UE. However, the MBSFN subframemay be allocated within the off durations. In this situation, the UE isunable to receive any data of the MBSFN subframe. As a result, the MBMSservice is interrupted.

SUMMARY OF THE INVENTION

A method of managing multimedia broadcast multicast service (MBMS)reception in a wireless communication system is provided to avoid theaforementioned problems.

A method of managing MBMS reception for a communication device in awireless communication system includes the step of performingdiscontinuous reception with off durations and receiving data of a MBMSsubframe when the communication device has subscribed a MBMS service andthe MBMS subframe is in one of the off durations.

A communication device of a wireless communication system for managingMBMS reception includes means for performing discontinuous receptionwith off durations, and means for receiving data of a MBMS subframe whenthe communication device has subscribed a MBMS service and the MBMSsubframe is in one of the off durations.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an exemplary wireless communicationsystem.

FIG. 2 is a schematic diagram of an exemplary communication device.

FIG. 3 is a flow chart of an exemplary process.

FIG. 4 is a flow chart of an exemplary process.

FIG. 5 is a flow chart of an exemplary process.

FIG. 6 is a flow chart of an exemplary process.

DETAILED DESCRIPTION

Please refer to FIG. 1, which is a schematic diagram of an exemplarywireless communication system 10. The wireless communication system 10,such as an LTE (long-term evolution) system or other mobilecommunication systems, is briefly composed of a network and a pluralityof user equipments (UEs) . In FIG. 1, the network and the UEs are simplyutilized for illustrating the structure of the wireless communicationsystem 10. Practically, the network comprising a plurality of basestations, such as an E-UTRAN (evolved-UTAN) comprising a plurality ofevolved Node-Bs (eNBs) in the LTE system. The UEs can be devices such asmobile phones, computer systems, etc. Besides, the network and the UEcan be seen as a transmitter or receiver according to transmissiondirection, e.g., for uplink (UL), the UE is the transmitter and thenetwork is the receiver, and for downlink (DL), the network is thetransmitter and the UE is the receiver.

Please refer to FIG. 2, which is a schematic diagram of an exemplarycommunication device 20. The communication device 20 can be the UE orthe network shown in FIG. 1 and includes a processor 200, a computerreadable recording medium 210 and a communication interfacing unit 220.The computer readable recording medium 210 may be any data storagedevice that stores storage data 212, including program code 214,thereafter read and processed by the processor 200. Examples of thecomputer readable recording medium 210 include a subscriber identitymodule (SIM), read-only memory (ROM), random-access memory (RAM),CD-ROMs, magnetic tapes, hard disks, optical data storage devices, andcarrier waves (such as data transmission through the Internet). Thecommunication interfacing unit 220 is preferably a radio transceiver forwirelessly communicating with other communication devices and cantransform process results from the processor 200 into radio signals.

Please refer to FIG. 3, which is a flow chart of an exemplary process30. The process 30 is used for managing multimedia broadcast multicastservice (MBMS) reception for a UE in a wireless communication system.The process 30 can be compiled into the program code 214 and include thefollowing steps:

Step 300: Start.

Step 302: Use a DL assignment to decode data of a MBMS subframe when aMBMS resource allocation and the DL assignment are received.

Step 304: End.

According to the process 30, the DL assignment is used to decode thedata of the MBMS subframe when the UE having received the MBMS resourceallocation receives the DL assignment. The DL assignment is dedicated tothe UE, and used for the MBMS subframe. In this situation, the UE canreceive the DL assignment on a physical downlink control channel (PDCCH)and determine the DL assignment has a higher priority than the MBMSresource allocation. On the other hand, the network may dynamicallyallocate non-MBMS data (e.g. uni-cast data) to the MBMS subframe if noMBMS data is transmitted in the MBMS subframe.

To receive the MBMS resource allocation, the UE preferably subscribesMBMS, or any service which may allocate MBMS resource allocation to theUE. The data of the MBMS subframe could be multicast traffic channel(MTCH) data, MBMS control channel (MCCH) data or dynamic schedulingdata, transmitted by the network in the MBMS subframe, so-calledmultimedia broadcast single frequency network (MBSFN) subframe. The MBMSresource allocation is received by broadcasting, such as from abroadcast message or system information of a cell broadcasted by thebase station, and may include a modulation coding scheme (MCS) andserving frequencies (i.e. sub-carriers) for MCCH, MTCH and dynamicscheduling information in a broadcast message (e.g. system information).Thus, when the UE receives two sets of decoding configuration for thesame MBSFN subframe (the DL assignment and the MBMS resourceallocation), the UE uses the DL assignment to perform decoding ofnon-MBMS data when there is MBMS data for transmission in the MBMSsubframe.

Please refer to FIG. 4, which is a flow chart of an exemplary process40. The process 40 is used for managing MBMS reception for a UE in awireless communication system. The process 40 can be compiled into theprogram code 214 and include the following steps:

Step 400: Start.

Step 402: Use a MBMS resource allocation to decode data of a MBMSsubframe when the MBMS resource allocation and a DL assignment arereceived.

Step 404: End.

According to the process 40, the MBMS resource allocation is used todecode the data of the MBMS subframe (e.g. MBSFN subframe) when the UEhaving received the MBMS resource allocation receives the DL assignment.The DL assignment is transmitted on the PDCCH by the network. The UE canfurther ignore or discard the DL assignment. Thus, the MBMS subframe canbe decoded through MBMS resource allocation assigned by the network.

Please refer to FIG. 5, which is a flow chart of an exemplary process50. The process 50 is used for managing MBMS transmission for a networkin a wireless communication system. The process 50 can be compiled intothe program code 214 and include the following steps:

Step 500: Start.

Step 502: Assign a MBMS subframe for transmitting non-MBMS data when thenetwork uses a MBMS resource allocation for transmitting MBMS data.

Step 504: Assign a dedicated-type resource allocation corresponding tothe MBMS subframe to a communication device of the wirelesscommunication system.

Step 506: End.

According to the process 50, the network first assigns the MBMS subframeto transmit non-MBMS data when using the MBMS resource allocation fortransmitting MBMS data, e.g. MTCH data, MCCH data or dynamic schedulinginformation. In the next step, the network can dynamically assign thededicated-type resource allocation to the communication device (e.g.UE). The dedicated-type resource allocation can be a DL assignmentdedicated to the communication device and indicates that the MBMSsubframe is assigned to transmit the non-MBMS data. The network canmanage which MBMS subframe MBMS data is not needed and thereby transmitnon-MBMS on the MBMS subframes that can be indicated to the UE throughthe resource allocation. This achieves cooperation with the UE formanagement of the MBMS reception.

In the LTE system, a discontinuity reception (DRX) function is appliedto a UE to reduce power consumption. The DRX function works withconsecutive DRX cycles each including an on duration and an offduration. During the on durations, the UE can receive control signals(e.g. PDCCH signals) from the network. When the UE subscribes MBMS andperforms the DRX function, the UE's behavior can be referred to FIG. 6,which is a flow chart of an exemplary process 60. The process 60 is usedfor managing MBMS reception for the UE in a wireless communicationsystem. The process 60 can be compiled into the program code 214 andinclude the following steps:

Step 600: Start.

Step 602: Receive data of a MBMS subframe when the MBMS subframe is inone of the off durations.

Step 604: End.

According to the process 60, when the UE has subscribed the MBMS serviceand the MBMS subframe is in any off duration, the UE wakes up during theMBMS subframe to receive the data of the MBMS subframe to avoid theinterruption of the MBMS service. In other words, during off durationsexcept the MBMS subframe, the UE enters a standby mode in which thecontrol signal reception is deactivated. For resource control in LTEsystem, the UE could be operated in a radio resource control (RRC)connected mode or in an RRC idle mode, herein.

In addition, when the UE wakes up, the UE can leave the off duration andturns on a receiver to receive the data of the MBMS subframe. As for theUE which does not subscribe any MBMS service, deactivation of the MBMSreception is remained during the MBMS subframe. In other words, the UEdoes not wake up if the UE does not subscribe the MBMS service. This canprevent the particular UEs from power consumption due to awakening.

Please note that the abovementioned steps including suggested steps canbe realized by means that could be hardware, firmware known as acombination of a hardware device and computer instructions and data thatreside as read-only software on the hardware device, or an electronicsystem. Examples of hardware can include analog, digital and mixedcircuits known as microcircuit, microchip, or silicon chip. Examples ofthe electronic system can include system on chip (SOC), system inpackage (Sip), computer on module (COM), and the communication device 20in which the processor 200 processes the program code 214 related to theabovementioned processes and the processed results can transfer thecommunication device 20 to a state of successfully decoding the MBMSsubframe that may carry non-MBMS data and successfully receiving MBMSsubframe data in the off durations.

To sum up, the above-mentioned examples specify the dedicated resourceallocation for the UE to decode received data of the MBMS subframe whenthe UE receives the downlink assignment on the PDCCH. This makes the useof the MBMS subframe more flexible. Correspondingly, the network assignsthe downlink assignment for the MBMS subframe to transmit non-MBMS datawhen the network uses the MBMS resource allocation for transmitting MBMSdata or dynamic scheduling information. In addition, the examples alsospecify the UE behavior, by which the UE wakes up for reception of theMBMS data during the off duration of the DRX cycle. This, thus, avoidsthe MBMS interruption.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. A method of managing multimedia broadcastmulticast service (MBMS) reception for a communication device in awireless communication system, the method comprising the step of:performing discontinuous reception (DRX) with consecutive DRX cyclesincluding off durations; and waking up to receive data of a MBMSsubframe when the communication device has subscribed a MBMS service andthe MBMS subframe is in one of the off durations; and deactivatingreception of control signal except the MBMS subframe during the one ofthe off durations; wherein each of the consecutive DRX cycles comprisesone on duration and one off duration.
 2. The method of claim 1 furthercomprising remaining deactivation of MBMS reception during the MBMSsubframe when the communication device does not subscribe any MBMSservice.
 3. The method of claim 2, wherein the communication device isoperated in a radio resource control (RRC) connected mode or an RRC idlemode.
 4. A communication device of a wireless communication system formanaging multimedia broadcast multicast service (MBMS) reception, thecommunication device comprising: a processor; a storage unit; and aprogram code, stored in the storage unit, wherein the program codeinstructs the processor to execute the following steps: performingdiscontinuous reception (DRX) with consecutive DRX cycles including offdurations; and waking up to receive data of a MBMS subframe when thecommunication device has subscribed a MBMS service and the MBMS subframeis in one of the off durations; and deactivating reception of controlsignal except the MBMS subframe during the one of the off durations;wherein each of consecutive DRX cycles comprises one on duration and oneoff duration.
 5. The communication device of claim 4, wherein theprogram code instructs the processor to further execute the followingstep: remaining deactivation of MBMS reception during the MBMS subframewhen the communication device does not subscribe any MBMS service. 6.The communication device of claim 4, wherein the communication device isoperated in a radio resource control (RRC) connected mode or an RRC idlemode.